A stage of this type comprises a distributor formed by a row of annular fixed guide vanes supported by a casing of the compressor or the turbine, and a rotor disk mounted upstream from the distributor inside a sectorized ring hooked on the casing.
The distributor comprises two respectively inner and outer annular walls, the fixed guide vanes extending therebetween.
The ring comprises, at one end thereof, a circumferential flange which is radially clamped on an annular rail of the casing through a substantially C-shaped cross-section annular locking device, which is axially engaged on the casing rail and on the circumferential flange of the ring. The locking device comprises two annular walls, respectively inner and outer, which are connected together through a substantially radial wall. This device is sectorized and made up of a plurality of locks circumferentially positioned in an abutting manner, each lock being generally engaged on the flange of only one sector of the ring and on a corresponding portion of the casing rail.
It is known that an annular sealing and heat shielding foil should be mounted between the downstream end of the ring and the upstream end of the outer annular wall of the distributor, notably to limit the radially outward leaks of hot gases flowing in the gas stream of the turbine or compressor and to thermally protect the locking device.
In the current technique, this foil is substantially cylindrical and interposed between the ring and the inner annular wall of the locking device. However, it is not correctly radially immobilized and can then vibrate in the operating state, and be damaged.
Further, each lock is engaged on the casing rail and on the circumferential flange of one ring sector with some radial preload. In the operating state, a radial gradient of a relatively substantial temperature appears in each ring sector, which causes a “discambering” of this ring sector. This phenomenon essentially produces into an increase of the curvature radius of the ring sector, which increases the strains in the median portion of the lock and can reduce its lifetime.